Off-center load moving assembly



July 4, 1967 Original Filed Nov. 1

R. R. TILLY OFF-CENTER LOAD MOVING ASSEMBLY 5 Sheets-Sheet. 1

INVENTOR RALPH R. TILLY ATTORNEY R. R. TlLLY July 4, 1967 OFF-CENTERLOAD MOVING ASSEMBLY Sheets-Sheet :2

Original Filed Nov.

FIG. 2 RAF I- I I RT T ILLY BY W I W O? 3 A fiRNfi y July 4, 1967 R. R.TILLY 3,329,029

OFF-CENTER LOAD MOVING ASSEMBLY Original Filed Nov. 1, 1963 5Sheets-Sheet J INVENTOR.

RALPH R. TILLY' BY WW 43 @P A TTORNE Y United States Patent 3,329,029OFF -CENTER LOAD MOVING ASSEMBLY Ralph R. Tilly, Webster, N.Y., assignoto Xerox Corporation, Rochester, N.Y., a corporation of New YorkContinuation of application Ser. No. 320,630, Nov. 1, 1963. Thisapplication Mar. 21, 1966, Ser. No. 543,469 1 Claim. (Cl. 74--89.15)

ABSTRACT OF THE DISCLOSURE Apparatus for vertically displacing anon-symmetrically distributed load along a vertically disposed rotatableshaft. Screw threads on the shaft are engaged by a shiftable threadedsleeve which is constrained against rotation. The threaded sleeve isfixedly secured with respect to the load as well as to a pair of annularsleeve bearings encompassing the shaft so that rotation of the shaft andscrew threads will axially displace the threaded sleeve, sleeve bearingsand load along the shaft.

This application is a continuation of my co-pending application SerialNo. 320,630 filed November 1, l963, now abandoned, entitled BearingAssembly.

This invention relates to an assembly for moving an off-center loadrelative to a vertically disposed rotatable shaft.

The movement of a load in a longitudinal direction along a verticallydisposed rotating shaft encounters frictional problems. The powernecessary to drive the load along the shaft must overcome both thefriction due to the sliding movement along the shaft and the frictiondue to the rotational movement of the shaft within the bearing. When theload being moved is off-center or nonsymmetrically distributed, thesliding and rotational frictional forces are further increased by themoment force or torque which tends to rotate the load. The invention,herein, is particularly useful for moving such a load where off-centerloading produces the large frictional forces.

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It is, therefore, the primary object of this invention to move a loadalong a rotating shaft.

It is another object of this invention to improve load moving apparatusto reduce the driving power necessary to move an off-center load in alongitudinal plane along a vertically disposed rotating shaft.

These and other objects of the invention are attained by mounting anon-symmetrical load on a vertically disposed rotatable shaft and havingapparatus operatively interconnecting the shaft and load so thatrotation of the shaft acts to turn a sleeve bearing inside a ballbearing and to raise or lower the load through a vertical plane bysliding the sleeve bearing along the shaft.

For a better understanding of the invention, as well as other objectsand further features thereof, reference is had to the following detaileddescription of the invention to be read in connection with theaccompanying drawings, wherein:

FIG. 1 is a front view of a xerographic reproducing apparatus, withcovers broken away, which is adapted to use the present invention;

FIG. 2 is a cross-sectional side view of the piece of apparatus shown inFIG. 1 and taken along lines 2-2 of FIG. 1; and

FIG. 3 is an enlarged cross-sectional view of the bearing assembly.

Referring to the figures, there is shown a piece of xerographicreproducing apparatus embodying the present invention. The apparatusused herein to illustrate the use of the invention is a large documentcopying apparatus which moves a document to be copied on a conveyor3,329,029 Patented July 4, 1967 and transmits a light image of thedocument through an optical system to a xerographic drum.

FIG. 1 shows a document conveyor 2, a xerographic drum 4, and an opticalassembly 6. The optical assembly 6 contains a pair of mirrors 8 and 10mounted above the conveyor and the xerographic drum, respectively. Themirrors 8 and 10 are mounted on a frame 12 which is supported by a leadscrew 14.

The lead screw 14 is rotatably supported in an upright position by apair of bearing assemblies 15 extending outward from a mast or column16. The bearing assemblies 15 are thrust bearings which prohibit anyvertical motion of the lead screw 14. The column 16 is mounted on theframe 18 of the apparatus and provides rigid support for the entireoptical assembly. In order to make enlargements or reductions of adocument on the conveyor system, it is necessary to vary the height ofthe optical assembly 6 and the length of the reflected light paththrough the mirrors 8 and 10. Therefore, the assembly 6 is supported bymeans of a nut or threaded sleeve 20 on a threaded portion 22 of thelead screw 14. When a document is placed on the conveyor, a pair offluorescent lights, not shown, illuminate a portion of the documentriding, vertically, on a guide post 21 secured to the conveyor. When thelead screw 14 is rotated, the frame 12 is prevented from rotating by therollers 19 and guide post 21 so that the lead screw rotates relative tothe nut 20.The rotational movement of the lead screw causes the nut 20and frame 12 to move in an upward or downward direction, thus extendingor shortening the reflected light path.

Rotational drive of the lead screw 14 is produced by motor MOT-1 throughgear box 24, pulley 26 and the belt 28 to a transmission 30. Thetransmission 30 is adapted to drive the lead screw in either directiondepending on whether upward or downward movement of the optical frame isdesired. A linkage 32 and two universal joints 34 and 36 connect thetransmission to the lead screw. As the lead screw is rotated, the nut ofthreaded sleeve 20 moves upward or downward depending upon the directionof rotation. As the nut 20 moves, it slides the optical assembly 6 alongthe shaft of the lead screw 14 on bearing assemblies 38 and 40.

The Weight of the optical assembly 6 is not uniformly distributed aboutthe lead screw 14. As can be seen in FIG. 1, the document conveyor 2 iswider than the xerographic drum 4 so that documents that are larger thanthe width of the xerographic drum 4 can be reproduced by reduction ofthe image size. Therefore, the mirror 8, over the document conveyor,must necessarily be larger than the mirror 10, over the xerographic drum4, and, likewise, the frame 12 must extend further from the lead screw14 out over the conveyor than the corresponding portion over thexerographic drum. This nonsymmetrical distribution of weight producesforces in the bearing assemblies 38 and 40 which would not normally beproduced if the center of gravity of the optical assembly 6 werecentered over the lead screw 14. As such, this peculiar weightdistribution exhibits a moment or force which tends to rotate the loador frame within the plane through which it is movable.

The nonuniform distribution of weight on the optical assembly 6 tends tocause rotation about the nut 20 and to set up nonvertical forces in thebearing assemblies 38 and 40. The actual forces produced in the bearings38 and 40 may be calculated by determining the distance from the leadscrew 14 to the point at which the total load of the optical assembly isconcentrated, by knowing the distance of each bearing from the nut 20,and by taking the summation of forces about a point, such as the nut 20.The moment forces produced in each of the bearings 38 and 40 increasesthe friction, both in the sliding movement and in the rotationalmovement of the shaft relative to the frame.

The torque required to drive the lead screw is increased by the torquenecessary to overcome the sliding friction and the rotating friction.Since the torque required to overcome the rotating friction is thelargest of the two, it is very desirable to reduce or eliminate thisrequirement. The bearing structure, shown in detail in FIG. 3,accomplishes this by using a sleeve bearing 42 on the shaft of the leadscrew 14 and a ball bearing 44 mounted between the sleeve bearing 42 andthe frame 12.

The sleeve bearing 42 is freely movable along the shaft. The inner race46 of the ball bearing 44 is mounted around the sleeve bearing and isretained by the shoulder 48. A snap ring 50, which fits in a groove 52,in the outer surface of the sleeve bearing retains the ball bearing inposition relative to the sleeve bearing. The outer race 54 fits into anannular shouldered groove 56 in the frame 12 and is retained therein byan annular retaining ring 58 fastened to the frame 12 by screws 60.

The shaft is freely slidable within the sleeve bearing 42 and the sleevebearing 42 is freely rotatable relative to the frame 12 by means of theball bearing 44. There is little or no relative rotary motion betweenthe shaft and the sleeve bearing since the friction between these twoparts is considerably higher than the friction produced in the ballbearing.

The rotational movement of the sleeve bearing 42 within the ball bearing44 reduces the rotational friction. The sliding friction of the sleevebearing relative to the shaft remains unchanged but, as pointed outabove, the larger portion of the load due to friction is produced by therotational friction and, with the use of the bearing described, therotational friction is virtually eliminated.

The sleeve bearing 42 is preferably a split bearing consisting of twohalves split longitudinally along the hearing. In the event that thebearing is to be replaced, the snap ring 50 may be removed and thebearing slid along the shaft and removed from the shaft withoutdisassembling the optical system.

While the present invention, as to its objects and advantages, asdescribed herein, has been carried out in a specific embodiment thereof,it is not desired to be limited thereby but it is intended to cover theinvention broadly within the scope of the appended claim.

What is claimed is:

Apparatus for vertically moving a load within a vertical plane, the loadbeing nonsymmetrically distributed so as to exhibit large rotationalforces within the plane through which it is movable, including a shaft,

positioning means adjacent the ends of the shaft to rotatably retain theshaft in a vertical orientation, fixed against axial displacement,

a pair of annular sleeve bearings mounted on the shaft between thepositioning means, the sleeve bearings being adapted for axialdisplacement along the shaft,

a threaded lead screw on the shaft located between the sleeve bearings,

a threaded sleeve encompassing the threaded lead screw, the threadedsleeve being held against rotation but free for vertical movement inresponse to rotation of the shaft and lead screw.

retaining means to hold the sleeve bearings, threaded sleeve and loadfixed with respect to each other, with the load located between thesleeve bearings,

ball bearing means rotatably securing each of the sleeve bearings to theretaining means, and

drive means to rotate the shaft and lead screw for vertically displacingthe load in response to the vertical motion of the threaded sleeve,sleeve bearings, and retaining means.

References Cited UNITED STATES PATENTS 1,212,353 1/1917 Hofferberth7489.l5 2,025,834 12/1935 Tautz 64-9 2,708,497 5/1955 Parrett 192982,986,430 5/1961 Banerian 30835 3,222,494 12/1965 OConnor 3086 FRED C.MATTERN, JR., Primary Examiner.

W. S. RATLIFF, Assistant Examiner.

